Hello, first: I messed up my site (images are not showing up), should be back to normal in 24 hours or so. Sorry for that.
Second. DeltaE is for me a question of trying the sliders, most of the time I manage to make a correct mask. If not, you can add the brush mask to erase some parts of the mask. I will write some more articles about masks, because it’s not always clear how they work or what they do exactly (including for me). Coming soon on a screen near you ! 